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28DL Full Member

Te disused Glynrhonwy Isaf slate quarry in North Wales which had closed in 1930, was deemed suitable for the storage of 18,000 tons of bomb during WW2. It consisted of a number of deep open pits, linked together by tunnels.

The lower level and a conventional flat reinforced concrete ceiling which also formed the floor of the upper level which had an arched roof. Standard and narrow gauge railway lines entered the lower level of the depot through the original quarry access tunnels, while three electric lifts transported bombs to the upper floor.

Overhead protection was given by forty feet of broken slate. In response to pressure from the treasury efforts were made to cheapen and accelerate the construction of Llanberis, but unfortunately the cost cutting had disastrous consequences only six months after the depot was opened. On 25th January 1942, two-thirds of the structure collapsed within seconds under the weight of the overlaying backfill, completely engulfing a train of twenty seven wagons which was in the process of unloading. The collapse buried over 14,000 tons of bombs which at the time represented 14% of the total RAF stock.

In 1969 a decision was taken to clear the entire site of explosives and explosive debris. From 1969 onwards, the various pits and tunnels were progressively cleared. Members of the EOD Flight burrowed further and deeper into the debris and slate rubble to uncover such items as incendiary bombs and high explosive bomb detonators.

Staff MemberModerator

The train and bombs were recovered during the war, and the tunnels were mostly cleared after the war in 1956 when the depot closed.

It was mainly the deep flooded quarry pits to the west of the depot that were used for burning and dumping redundant and dismantled ordnance. In 1969 a decision was taken to clear the entire site of explosives and explosive debris.

The task was given to 71 Maintenance Unit EOD Flight RAF assisted by 33 EOD Regiment RE & 38 Field Engineer Regiment RE. The task was completed in October 1975.

The following text was taken from the book 'Designed to Kill' by Major Arthur Hogben, ISBN 0850598656

Probably the largest land clearance task in respect of the weight of ordnance recovered was that at Llanberis. Royal Air Force Llanberis was opened as an explosive storage unit in May 1941, close to the Snowdonian village of that name in north Wales. The site occupied a large complex of disused slate quarries and interlinking tunnels. Between 1941 and July 1956 when the unit closed it had been used as a bomb store, a demolition area and a burning pit.

The demolition and burning of explosives within the quarry area started in June 1943 when the Royal Air Force School of Explosives moved to the site.

The school curriculum included the destruction of explosives, so large quantities of bombs and pyrotechnics were brought in for demolition or burning.

The destruction of explosives continued until July 1956 when the unit was closed. Included in the destruction programmes were virtually every type of explosive item on the Royal Air Force wartime inventory.

Unfortunately, as sometimes happens with mass demolition, a proportion of the items were not completely destroyed. Thus this large and practically inaccessible complex of quarries was known to contain quantities of explosive items. As such the site solicited a certain amount of indiscriminate dumping of unwanted or recently recovered explosive items.

The shape of the site was such that much of the explosive material dumped ended up on ledges and slate outcrops, never reaching the quarry bottoms. More still had been dumped or fallen into the lakes, which had formed in the quarries during the years of inactivity between 1956 and 1969.

It was in this latter year, 1969 that the decision was taken to clear the entire site of explosives and explosive debris. The task was given to 71 Maintenance Unit EOD Flight from Royal Air Force Bicester (later to be designated No 2 EOD Unit, RAF).

By the time the task was completed in October l975,the personnel of the Flight had become expert in lifting tons of explosives from the quarry pits and lakes and in the handling of special mechanical equipment. They had also learnt the arts of tunneling and rock climbing, which in the earlier days had been the only ways of gaining access to some of the pits and their surrounding ledges.

This must have been one of the few bomb disposal tasks carried out by any Service where members of the unit had first to be instructed by a Mountain Rescue Team. The various rock climbing techniques and rescue procedures taught were essential to enable members of the unit to reach much of the explosive ordnance with which they had to deal.

From 1969 onwards, the various pits and tunnels were progressively cleared. Members of the EOD Flight burrowed further and deeper into the debris and slate rubble to uncover such items as incendiary bombs and high explosive bomb detonators. The latter, together with the numerous bomb fuses, which were uncovered, were in an extremely hazardous condition and required careful handling.

With the help of the Royal Engineers, roads were constructed into the more difficult pits and the' fly on the wall' approach became less frequent. However, at no time throughout the six years of the project was the task rated any easier than' very difficult '. It was not a question of true grit and stamina, but rather an excess of slate, grit and slime.

Royal Navy divers were co-opted to investigate the contents of a large lake in one of the pits as it was suspected that it might contain some explosive items. The divers reported that the bed of the lake was littered with explosive items including a number of large bombs.

Subsequently, over 20,000,000 gallons (90,920,000 liters) of water and sludge were pumped out. By April 1973 the lake was emptied revealing everyone's worst fearsâ€”it took a further two years of hard labour to recover and dispose of the explosive items revealed. Fortunately, this pit was one of those to which 38 Engineer Regiment, RE, had constructed a road, otherwise the task would have been impossible.

On completion of the task, 71 Maintenance Unit EOD Flight had moved approximately 85,000 tons (83,364 tonnes) of slate and debris, recovered and disposed of 352 tons (357 tonnes) of explosive items together with 1,420tons (1,443 tonnes) of non-explosive ordnance debris.

Many people were involved in this task, too numerous to quote by name, but a few who played a prominent part deserve to be mentioned. Those directly involved at the work face were Flight Lieutenants E. S. T. Tout, W. Jones and J. Thomson, RAF, all of whom successively commanded the EOD Flight concerned. In the early day s of the task the workforce consisted of an eight-man team headed by Flight Sergeant Russell, RAF, who was awarded the Medal of the Order of the British Empire (BEM) for his work during the initial opening up of this extremely hazardous operation. Other senior non-commissioned officers involved at some stage or other in the project were Flight Sergeant G. Twine, Flight Sergeant E. K. Tumman, BEM (who moved to Llanberis direct from the Maplin Sands task), Chief Technician D. Andrews, BEM, and Sergeant B. Rutter (who was later killed whilst clearing British cluster munitions following a trial drop).
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